Catalytic cracking



l `8, l1942. o. F. CAMPBELL Y 2,304,397

. CATALYTIC CRACKING Filed Aug. 16, 1939 4 sheets-sheet 1 Dec. 8, `194:2. o. lr-. CAMPBELL y 2,304,397

CATALYTIC CRACKING Filed Aug. 16, 1939 4 Shets-Sheei 2 INVENTOR Ulli/ef (am/05d! BY ATTORNEY Dec. 8, 1942.

o. RCAMPBELL CATALYTIG CRACK-ING Filed Aug. 16, 1939 4 Sheets-Shes?l 3 ATTORN EYS De. 8, 1942. o. F. CAMPBELL 2,304,397..

CATALYTIC cRAokING Filed Aug. 16, 1939 4 Sheets-Sheet 4 ATTORNEYS Patented Dec. 8, 1942l OFFICE caratmc casema oliver F. campbell, Whiting, 1nd., assignito Sinclair Refining Company, New York, N. Y., a

corporation of Maine Application August 16, 1939, Selfil N0. 290,398

13 Claims. (CL 196-52) i be reached in a very short time, even in a few This invention relates to catalytic cracking of hydrocarbons and provides `improvements in a method for cracking higher-boiling hydrocarbons `to produce more valuable lower-boiling hydrocarbons in the presence of a catalyst.

In heretofore customary operations, the cata- `lytic treatment of the hydrocarbons has .been conductedin an intermittent manner. The hydrocarbons to be cracked, for example a petroleum stock, are vaporized by heating under a low pressure, usually in the presence of steam to promote vaporization. 'I'he temperature of the resulting vaporous mixture of hydrocarbons, and any steam, may range from '100-800 F. to about 1000-1100" F.; the pressur may range from sub-atmospheric to as high a 100 pounds per square inch or more. Depending upon the nature of the stock to be cracked, the temperature and pressure, and the proportion of steam employed, all or only a portion of the stock may be vaporized. When unvaporizedhydrocarbons remain these are usually separated and removed prior to catalyst contact. In any event, the vaporized hydrocarbons re sent to the cracking operation. There, in a r of the hydrocarbon vapo is passed in contact with a solid and usually porous or granular catalytic-mass, such, for example, as fullers ous metals or metal salts. Lower-boiling hyction zone, a stream' drocarbons and carbon\ result fromthe ensuing cracking. The lower-.boiling hydrocarbons and some of' the carbon are removed from the reaction zone as formed, but a substantial portinof the carbon adheres to thecatalyst and coats its surfaces and chokes its pores as it accumulates As the carbon accumulates and fouls the catalyst, the activity of the latter decreases.' When the economic limit of catalyst activity has been reached, the stream of hydrocarbon vapors to be cracked is diverted to another reaction zone containing a reactivated or f is exothermic.

seconds, andin certain catalytic cracking operations, the entire cycle time for cracking and regeneration may be less than a minute. This has necessitated the development of elaborate control mechanisms for automatically bringing about diversion of the stream of stock from a fouled catalytic mass to a regenerated one. Suc'h control mechanisms not only increase plant investment and maintenance costs, but are subvject to operating diiiiculties.' The regular pro-y duction 'of superior cracked products requires uniform operating conditions.

The heat of the cracking reaction is composed of the heat of decomposition and the heat of recombination. Decomposition is endothermic and recombination is exothermic, and whether or not the reaction as Va whole is heat-releasing C the stock itself, or from an exterior source as regenerated catalyst mass, and the fouled mass is subjected to regeneration. This is usually accomplished by passing a hot oxidizing gas in contact with the catalyst so as to burn oir the carbon accumulated on the surfaces and yin the pores thereof and thus clean the catalyst for further service. Once the: catalyst has been reactivated or regenerated by such treatment, the 50 stream of vapors to be cracked is ultimately diby conduction through the walls of the cham.

ber in which the catalyst is'conilned. Qnr the other hand, regeneration involving as it does combustion of carbon, is 'exothermia and its.suc cessful accomplishment requir dissipation of heat. This situation is one in which heat exchange between the cracking zone and the zone of regeneration is desirable, but such exchangel 's has heretofore been accomplished only at the .as the catalyst requires'regeneration, which permits aV substantial gain in thermal eillciency through improvedl heat exchange betweenthe cracking and regenerationphases of the cycle` and which aifordsseveral advantages with respect to control.' consequent upon these limprovements, the cumbersome automatic controls;

- zones so that individual segments of the catalyst mass pass successively and cyclically through a first zone to which the vaporized hydrocarbons to be cracked are supplied substantially con, tinuously and fromwhich the resulting cracked hydrocarbons are withdrawn substantially continuously, a second zone through which a purging fluid (such, for example, as super-heated steam) is passed substantially continuously, a third zone through which a hot oxidizing gas is passed substantially continuously and in which the carbon deposited on the mass is burned away and a fourth zone through which a purging fluid is passed substantially continuously to remove -products of the carbon combustion from the mass prior to the reintroduction thereof into the first zone, while substantially uniform conditions are continuously maintained in all four zones, particularly the rst.

These The above described method may be carried on in a variety of apparatus, but is advantageously-performed in the apparatus described and claimed in my copendingapplication Serial No. 290,399, filed August 19, 1939, now U. S.

APatent 2,246,345. This-apparatus provides a casing divided into at least a cracking section and a regenerative section by radially extending baffles. These sections` are sealed from each other, but enclose a concentrically. mounted wheel divided into a pluralityof segments in each of whichI is disposed a catalyst. The Wheel is rotatable with respect to the various sections which enclose it, so that its catalyst segments 'I may be passed continuously through the series of sections and thus be alternately employed to crack hydrocarbons passing continuously through the cracking section and be regenerated by hot oxidizing gases in the regenerative section. More specifically, the invention provides, conducting a process for the catalytic cracking of hydrocarbons, in apparatus having the combination which comprises a hollow and preferably annular head divided around its periphery into a plurality of segmental chambers, said head having a fiat bearing plate with ports therein communicating, respectively, with each of s aid chambers, a second hollow head (preferably a mirror-image of the first) disposed concentrically to the first head and having segmental chambers matching those in the first head with a iiat bearing plate having ports therein corresponding to those in the first head, said bearing plates being displosed concentrically and parallel facing each other and spaced apart a fixed distance, a catalyst 'carrier in the form of a wheel disposed vbetween the two bearing plates with its axis coinciding with that of the two heads and rotatable relative to the I heads, said carriery being divided into a plurality of segments or compartments by radial vanes extending substantially from 'one bearing plate to the other, a catalytic mass disposed in the compartments of the catalyst carrier, means for forcing vaporized hydrocarbons from a chamber of one lhead to a corresponding chamber of the other head in contact with the catalytic mass in a compartment, means for simultaneously forcing a hot oxidizing gas from a second chamber of one head to acorresponding second chamber of the other head in contact with the catalytic mass in another compartment, and means for simultaneously rotating the wheel relative to the heads.v

In the preferred form of the vapparatus for conducting the preferred mode of operation of my invention, the heads are annular; the catalyst carrier is rigidly mounted on a shaft disposed.

on the common axis of the two heads and passing therethrough; means are provided for rotatl ingA the shaft; means are provided for preventing leakage of vapor between the various sections of the apparatus, and the catalyst carrier is surrounded by an annular jacket for a hot diluent gas such as steam. The jacket space is enclosed by a drum fastened to the two heads so as to enclose the carrier, and means are provided for supplying the diluent gas (say steam) to the jacket at a pressure in excess of that prevailing in any of the chambers so that leakage of gas, if any, will take place into the carrier compartments rathers lthan out, thereby preventing leak- 'age to the outside and undesirable admixture of hydrocarbons and oxidizing gases within the apparatus.

There may be two or more chambers in each of the heads but preferably there are at least four, comprising, respectively, along the direction of rotation of the apparatus a chamber for hydrocarbons, a second for a purging gas such asvsteam, a third forf the oxidizing gas and a fourth for a purging gas to remove the products of oxidation.

The number of compartments or segments in the catalyst carrier may be two or more, but preferably a large number (such as eighteen or twenty) is provided. In any case, the segments shouldbe of such .dimensions relative to the radialA distance 'between the ports in the bearing plates that no one catalyst segment is in contact with the ports .of different chambers in the samehead at the same time; that is to say a segment should be out of contact with the port supplying hydrocarbon before it comes in contact with the port which supplies purging gas, etc. This may be assured by making the radial space between ports, i. e., the distance between them in the path .of rotation, greater than the radial space or angle devoted to a single segment.

These and other features of my invention will be more thoroughly understood in the light of the following detailed description taken vin conjunction with the accompanyingdrawings in which Fig. 1 is a plan view of apparatus for carrying out the process of my invention having means for rotating a catalyst successively through a cracking zone, a purging zone, a regenerative zone, and a second purging zone;

Fig. 2 is a vertical section taken throughl the apparatus of Fig. 1 along the section line 2 2;I

L disposition of the rotating catalyst apparatus of Y larly` to Figs. 1, 2 and 3, it will be observed that in general the apparatus comprises `a vertical shaft assembly I upon which is rigidly mounted a substantially cylindrical catalyst carrier wheel II. The outer portion of the carrier wheel is enclosed by an annular casing I2 which is circular in plan and comprises a central cylindrical drum portion or jacket I3 to which isl fastened at the top and bottom, respectively, a pair of hollow annular heads I4, I5. The inner wall of each head is formed. by fiat annular parallel bearing plates I6, I1`. The heads are mirror images of each other and each is divided into four sections by radially extending baflles. These sections correspond to a cracking zone I8, a first purging zone I9, a regenerative zone 20 and a secondV purging zone 2I (FigLB). The carrier wheel is adapted to rotate successively through these zones, carrying catalyst segments mounted thereon in contact with the hydrocarbons to be cracked, thence' into contact with'superheated steam or other purging gas in the rst'purging zone, thence into contact with an oxidizing gas in the regenerative zone and again into contact form a cooling water chamber' 26. A water inlet pipey 21 projects upwardly from the base of the shaft to a point adjacent its closed upper end 28. This pipe is stationary. Water forced into it through a lower water inlet 28, enters the cooling water chamber and flows downwardly ,through the lower hollow portion 30 of the shaft into a water outlet gland 3l disposed below the thrust bearing and concentrically aroundthe water inlet pipe.

The lower portion of theV shaft lis, rotatably mounted on-this gland, thus forming a sealedsystem. Water forced through the inlet pipe cools the .interior of the shaft, flows downwardly through a rotatable coupling 32 disposed below` the thrust bearing and out through the gland.

The carrierwnen Il is rigicuy fastened to the shaft adjacent its enlarged portion. Immediately Each seal member has a series of concentric cir- 1 cular grooves 4I, 42, 43 and 44, 45, 4611i the surfaces that face the plates, and into these t a series of corresponding'rings'", 48, 48 and 50, 5I, 52 that are fastened to the plates of the two casing heads thereby forming a pair of peripheral labyrinths, 53, 54, respectively, at the upper and lower outer edges of the catalyst carrier wheel;

The space between the sheath and the outer shell of the carrier wheel is divided into a plurality of segmental compartments 55A, 55B, 55C,

`et seq: to 55R by vertical radial baiiles or vanes 56A to 56H. inclusive (Fig. 4). Any desired number of compartments may be provided, but it is desirable 'to have a relatively large number of them, and, in the instant case eighteen compart-I mentsare provided. The vertical baffle plates extend substantially completely from' top to bottom of the carrier wheel and have straight horizontal upper and lower edges 51, 58 close to and parallel with the inner surfaces of the bearing plates ofthe two heads. In the lower portion of each compartment a horizontal foraminous plate 59 vor other catalyst support is fastened.

`.A porous or loose granular catalytic mass B0 or bed is disposed in each of the segmental com- It may be composed A number of such materials are known, amo g them being kieselguhr or fullers earth. The catalyst bed substantially fills the segmental compartments to a point just below the `upper edge of -the vanes. The catalyst bed should be porous or otherwise designed to permit the pasd sage of gasefs therethrough in a vertical direction.

It will be observed that around' the -catalyst carrier wheel between itsouter shell and the drum portion I3 4of :the casing there is an annular chamber il. This annularchamber or 'jacket space is enclosed at its upper and lower ends by the peripheral seal. members.` However, unless these seals are perfect thereis, a tendency for gas under pressure to leak through the annular space from one head to the other 'and thus byepass the catalyst bed. With a view toward preventing such by-passing 'and also maintaining a proper temperature within the apparatus, steam is admitted vinto the annular chamber through a pipe 62, the

pressure of the steam being in excess of thatmaintained within the apparatusuas a whole so `that any leakage which occurs will be of steam I from the annularl chamber 'into the space occupied bythe carrier wheel and the upper and lower heads. A

An inner pairvl of peripheral labyrinth seals 53, 54 is provided, respectively, at the top and bottom of the carrier disk adjacent the space lled adjacent the shaft, the carrier wheel has an top and bottom of the shell 38 arefastened, re,l

spectively, outwardly. projecting Aperipheral lab'yf rinth seal members 38, 40. These-members are 4. disposed adjacent the plates I6, I1 that form the with insulating material. In this instance, a series of concentrica-lly disposed rings A, 65, 65, and l68, 69, 10 are fastened, respectively, to the upper and lower surfaces ofthe carrier wheel on the plates 35, 36 and project intoperipheral concentric grooves 1IA, 1I, 12, and 14, 15, 16 formed in a pair of upper and lower bearings 11, 18

through which the shaft passes. The labyrinthA -seals 63, 34 or other sealing device of like form, Y

are necessary to prevent leakage of gases from the space above andobelow the catalystebed outwardly to the atmosphere. If desired, packing material may be placed in the seals.

To consider the construction of the upperand lower heads I4, I5 of the casing, reference vshould walls =oi. the upper 'andlower heads, respectively. 76 beniade particularly to Figs. 2 and 3. 'The upper ameter.

-remote from the carrier wheel are formed of curved plates '|9, 80. These are welded to the inner flat annular bearing plates I6, Each of vthe annular chambers 8|, 82 thus enclosed is divided into at least four'segmental chambers by vertical radially extending bales. 'K

Thus, the chamber 8| of the upper head is divided iiito a hydrocarbon chamber 83, a rst steam chamber 84, an oxidizing gas chamber 85 and a second steam chamber 86 by batlles 8l, 88, 89, 90, and these chambers are. disposed, respectively, in the cracking zone I8, the first purging zone |9, the regenerative zone 20, and the second purging zone 2|. Likewise, the interior 82- of the lower head is divided into four corresponding segmental chambers 9|, 92, 93, 94 by bailes 95, 96, 91, 98,A (see Fig. and these chambers are disposed, respectively, in the cracking zone, the rst purging zone, the regenerative zone and the second purging zone.

The rotation of the carrier wheel is clockwise as viewed from above. Thus, as the wheel is rotated, any segment of the catalyst bed passes successively between thechambers' 83, 9|, or hydrocarbon chambers of the upper and lower heads, be-

; tween the chambers 84, 92 or first steam chambers, between the chambers 85, 93 or oxidizing gas chambers, and between the chambers 86, 94 o second steam chambers.

As illustrated in Figs. 3 and 5, the hydrocarbonY respective cked enter chambers occupy more than 71g of t heads. Hydrocarbon vapors to be c approximate in cross section about ve or six catalyst segments and are spaced from adjacent ports by a distance equal to more thanone of the segmentsof the catalyst wheel, for reasonshereinbefore explained. Hot air or other oxidizing vgas for burning carbon from the catalyst segment is admitted into the upper chamber 85 through a pipe |09, passes downwardly through the rotating catalystsegments into the corresponding lower chamber 93 of the lower head and is withdrawn therefrom through an outlet pipe H0.

The balance of the apparatus is occupied by the second -purging section. This second purging section, like the first, corresponds radially to two or three of the catalyst segments. It contains the second steam chambers 86, S0 in the upper and lower heads, respectively. Steam for purging is admitted into the upper chamber 'ing section are provided with small pie-shaped ports ||3, H4 (equal to about one catalyst segment) through which the steam passes into and out of the catalyst segments.

To prevent leakage between the various sections of the apparatus, the upper and lower edges of cach o -f the vanes onthe catalyst carrier wheel are provided with wiper seals which bear against the inner plates of the upper and lower heads.

. Such a seal is shown in detail in Fig 6, and comprises a flexible brush H5 fastened to the vane y and bearing against the inside plate of the head.

the upper hydrocarbon chamber 83 through a feed pipe 99 of relatively large diameter, pass from this chamber through a port |00 that corresponds in radial space to ve or six catalyst segments, through these catalyst segments and a matching outlet port |0| into the lower hydrocarbon chamber 9|. The resulting lower-boiling hydrocarbons are -remo from this chamber 9| through an outlet pipe |02 of relatively large di- Adjacent the hydrocarbon chambers, 84l 92 of the respective heads are the first steam chambers )which occupy 8/18 or -/lg of the respective heads.

Steam is admitted into the upper chamber 84 through pipe 84A, and passes into contact with the rotating catalyst carrier through a small port e |03 in its bottom or bearing plate. This port is equal radially to about one catalyst segment and is disposed in the approximate centerof the plate. The steam port |03 is separated from the hydrocarbon port |00 by a radial distance greater than that of one catalyst segment, so that such a segment must pass out of contact with the hydrocarbons before steam is admitted thereto. There is a corresponding steam port |04 in the plate of the matchinglower steam chamber 92. Steam isad- Seals of diiTerent construction may, ofcourse, be provided, but that illustrated is simple and eective.

The upper head is provided with four thermocouples IIB, ||8, ||9 disposed, respectively in wells |20, |2|, |22, |23 in each ofthe several chambers to enable proper temperature control of the system. Like thermocouples in similar wells are provided in the several chambers of thelower head. l

A better idea of the operation of the apparatus i described hereinb'efore may be obtained by reference to Fig. 5 which is a developed diagram o f'the apparatus. Referring now to this diagram, it will be observed that oil vapor to be cracked is admitted in the hydrocarbon chamber of the upper head. It passes from this chamber through the hydrocarbon port. (corresponding to about six segments of the carrier), through.

these six segments and the corresponding lower .hydrocarbon po'rt into the lower hydrocarbon chamber from whence it is withdrawn.y

mitted into the upper chamber 84 through apipe 84A, and-withdrawnfrom the lower chamber 92 through a pipe |06.

Next around the periphery of the apparatus vis the regenerative section in which are disposed the oxidizing gas chambers 85, 93.' 'I'hese cham'- bers occupy approximately @i8 -to 7/18 of the respectiveupper and lower heads. They are provided with a pair of segmental ports |01, |00, respectively, in the upper and lower plates through which hot oxidizing gases pass for contact with4 the catalyst segments to be regenerated. The

ports in the regenerative section of the apparatus At the same time, steam is passed through thel rst purging section, entering rst the steamI compartment of the upper head, passing then through a smallport (equal to about one catalyst' segment) and thenthrough the catalyst segment and the lower port into the steam chamber in the lower head. 'Ihe steam, plus such substances as have been purged from the'catalyst (principally entrained hydrocarbon gas) is withdrawn from the chamber in the lower head either independently or together with the cracked oil vapor from the cracking section, v Simultaneously, hot air plus steam or inert ga is introduced into the regenerating section which corresponds in this case to about six catalyst segments. 'Ihe mixture of steam or inert gas with hot' air enters the oxidizing 'gas chamber of Asegments are being subjected to contact with oil vapors, others to contact with steam in the iirst purging section `and still others to contact with hot oxidizing gas in the regenerative section, the balance of the catalyst segments are being treated in the second purging section with steam which is admitted into the upper head in its steam chamber corresponding to about two catalyst segments from whence it passes to a port corresponding to about one catalyst segmentl and `through this catalyst segment and the correspending lower port into the lower steam chamber from whence it is vwithdrawn either alone or with the exhaust gases of the regenerativel section. As shown in Fig. a control valve |24 is pro- `vided on the inlet line 99 for regulating the paspurging sections so that gases therefrom may be passed through by-pass lines |34, |35 and mixed,

' if desired, with the products ofthe cracking and :regerenative sections or else handled separately. Thus, the valves |30, 3| on the outlet of the first purging section permit exhaust gases therefrom supplying media'in thepurging and regenerative sections of the apparatus, an amount `of heat can be stored in the rotating catalytic segments which will be :lust sufiicient to siipply that necessary for the cracking reaction.

In the event that the cracking reaction is exothermic, the rotating catalyst segments are cooled in the zones other than the cracking zone, and are returned to the latter at a temperature below that prevailing in the cracking zone. so

to be mixed with the product of the cracking section or handled independently. Likewise, the

valves |32, |33 on the outlet of the second purg- 4 outery casing of the apparatus may be covered I with a heat insulating jacket |31.

As indicated hereinbeforef the cracking reac- Y tion ordinarily is endothermic but may become exothermic at temperatures in excess of about 975 F. and with certain stocks when the heat of ,recombination exceeds the heat'lof decomposition. Hence, in most instances', it is necessary to add heat tothe cracking zone, but with certain 'stocks and under certain conditions it may be` necessary to extract heat. In either case, the method herein-described provides 'convenient regulation of the heat supplied to the cracking zone or removed therefrom, by varying the amountl of heat contained in the rotating catalyst segments.

that they act to extract heat.

The heat supplied and extracted from the rotating catalytic segments in the various zones will, of course, depend upon the specific heat, i. e., the heat containing capacity of a given mass of the catalyst per degree temperature, as well as upon thermal gradients existing between the several zones and the catalyst segments passing therethrough. Consequently, the catalytic mass should have a relatively high specific heat and the mass itself should be large enough to assure ample heat carrying capacity. i

Assuming that the catalyst segments are such as to carry an adequate amount of heat to or from the cracking zone, the regulation of the amount of heat so carried can be controlled in various ways. If gases of constant specic heat, temperature and volume are passing through the purging and regenerative sections, the amount of heat supplied to the cracking zone may bealtered by varying the speed of rotation of the catalyst ca rrier. On the other hand, the amountl of heat introduced into the catalyst carrier and This regulation may be brought about by changi ing the temperature or the specic heat or both 45.

of the gases passed through the regenerative zone.v regenerative zone cannot be regulated without regard to the oxidizing characteristics or capacities of the gases passing therethrough. Consequently, it is convenient vto provide, as illus- -itrated in Fig. 5, a source of hot oxidizing gas and of a hot diluent or inert-gas, which may be inert carbonaceous gaseous products of combustion correct oxidizing characteristics concurrentlywith the proper speciiic heat and temperature.V

This condition havingbeen attained, and assuming the correct speed vof rotation of the catalyst carrier, the exacty amount of heat necessary for the promotion of the catalytic cracking reaction maybe supplied. By this means constant If, for example, the particular cracking reaction being carried out is strongly' endothermic,

it is necessary to supply to the cracking zone a relatively .large amount of heat. In accordance with my invention, this heat i's supplied by the in addition to acting as catalysts. 1Bl' Proper conditions can be maintained in all ofthe zones sired speed of ro ation for a given stock has been.

established, the \h`aracter and amount of oxicontrol of the speed of rotation and of the heat However, this regulation of heat in the f mass.

' dizing gas employed in reactivation may be cont'rolled so as to burn from the catalyst the Hesired proportion of the carbon content deposited thereon. Regulation of the proportions of inert diluent gas and air in the rnixture supplied to the reactivating zone to increase the ratio of the former to the latter tends to decrease the rate of carbon combustion and vice versa. Thus, if desired, all of the carbon may be burned out of the catalyst. However, it is preferable to burn substantially only the surface carbon from` the catalyst, leavingl some deposit of carbon within the pores of the mass. Operations so conducted result in an increased yield of more valuable hydrocarbons with a minimum degradation or conversion of hydrocarbons to elemental carbon.

In the event that the heat of reaction cannot be supplied in the reactivation zone either from theheat of combustion, orfrom the sensible heat of gases introduced therein while maintaining an optimum catalyst eiciency, the apparatus may be divided into five sections rather than four, the additional section being used for raising or lowering the temperature of 'the catalyst bed by means of steam, 'inert gas, or by passing the gaseous products of reactivation through the Moreover, by varying the temperature and quantity of preheated steam or other purging gas passed through the4 purging section, the amount of heat picked up by the rotating catalyst may be varied to some degree.

As indicated hereinbefore, the sealing steam introduced into the 4jacket space between the catalyst wheel and the drum of the casing tends .'to leak into the oil vaporibeing cracked as well as into the inert gas or steam-air mixture passed through the regenerative section. For this reason, the steam employed for sealing should be maintained at a temperature sufiiciently high that leakage thereof into the apparatus will not reduce the temperature of the vapor streams, especially thestream of hydrocarbons. Hence, it is necessary tosuperheat the steam employed for sealing to a temperature slightly in excess of that of the oil vapors being treated in the cracking zone. Superheating the steam offers a further advantage by serving to reduce the amount of steam required for sealing.

In order to minimize steam consumption in the apparatus and especially steam consumption due to leakage, it is desirable to maintain the pressure of the gases employed in reactivation substantially the same asv the pressure of the oil vapor entering the cracking zone whilev maintaining slightly higher pressures on the steam -entering l the purging zones and the sealing zone.

To minimize leakage from zone to zone at the bottom of the carrier wheel a back-pressure should may be varied inversely to the air supply sa as to maintain a substantially constant volume ilow- 'ing` through the catalyst. This will permit the maintenance of a pressure drop through the reactivation zone equivalent to the pressure drop of the oil vapors passing through'the cracking zone. The valves provided in the apparatus, as illustrated in Fig. l5, permit such variations.

Generally speaking, the portion of the apparatus employed as a regenerative zone should be approximately the same in size as that employedA` in cracking and both should occupy several times as much space as the purging sections.

dividual segment of the catalyst carrier must pass I completely out from under a port into the cracking zone before it passes under the portin the iirst purging zone, et seq.

The apparatus of Figs. 1 to 6 may be incorporated into a variety of hydrocarbon cracking ture is sent to a dash tower |60A.

systems, and utilized in conjunction with a variety of equipment for recovering and separating the cracked hydrocarbons. One means of utilizing the apparatus is illustrated in Fig. 7 which is a flow sheet of a catalytic cracking system including the rotating catalyst apparatus hereinbefore described. In this system, a petroleum stock to be cracked is mixed with an appropriate amount of steam |5| and the mixture is passed to a heater |52 which vaporizes the oil substantially completely. From the heater a mixture |53 of oil vapor and steam (say in equimolecular proportions) passes to a cracking apparatus 5d, constructed as described in detail hereinbefore and indicated diagrammatically on Fis.` 7. The oil vapor and steam mixture passes through the cracking section of the apparatus as the catalyst carrier thereof is rotated (at a speed of, say, two revolutions per minute) and the oil is cracked and withdrawn in a mixture |55 of steam and vapors of lower boiling hydrocarbons at the lower portion of the apparatus.

A supply of steam |56 for 'operating the purging sections of the cracking apparatus, for admixture with hot air for the regenerative section and for sealing purposes is passed through a superheater |51, and there heated to a temperature in excess of that of the oil entering the cracking section. Part of this superheated steam is passed through a line |58 into the space between the catalyst wheel and the drum of the casing, from which it may leak through the labyrinthian seals into any of the sections of the apparatus but in so doing prevents leakage outwardly from these sections. vAnother part of the superheated steam passes through a line |59 into the first purging section of the apparatus and sweeps out of the catalyst segments that rotate there through residual oil vapors.A The steam from the rst purging section is permitted to intermingle with the cracked hydrocarbons exhausted from the cracking apparatus to form the mixture |55 and through a pipe line |60 the mix- A third portion of the steam from the superheater may be mixed with hot compressed air and inert gases in a pipe line |6| and passed through the regenerator section of the cracking apparatus. To produce the hot compressed air, atmospheric air is rst compressed in a'compressor |62, passed through a heater |63 and thence into the "the top of this column.

line |6l. 'I'he inert gases for diluting the air and thus impeding the combustion of the carbon on the catalyst segments passing through the regenerative section may be produced by burning carbonaceous fuel |64 in hot compressed air delivered to an inert gas generator |65 through a pipe line |66. From ther` inert gas generator the inert gas, in which the oxygen has been substantially all consumedis sent into the pipe line |6|. Superheated steam is admitted to the second purging section through a conduit |61, and after passing through the rotating catalyst segments is withdrawn from the lower head and may be passed to waste either independently or mixed with the exhaust gases from the regenerative section through a stack |68. When the petroleum stock to be crackedv is a relatively light oil which can be completely vaporized under prevailing temperature `and pressure conditions, say a temperature ranging from 800 to 1000" F. and a pressure ranging from sub-atmospheric to in excess of 100 lbs. per sq. inch, it is not necessaryto remove unvaporized hydrocarbons prior to introduction of the mixture of oil and steam into the cracking apparatus. Otherwise, a flash chamber (not shown) should be disposed between the heater and the inlet for the oil vapors into the cracking apparatus. I

If desired, one or more of the crackingapparatusor units may be connected in parallel or in eries. In any event, the outlet from the crackng sections of the apparatus augmented by purging and sealing steam, all at a temperature loi? about '150-1100 .F. and preferably between 800-1000 F. is sent to the iiash tower |60A without release of pressure. l

The flash tower temperature may be controlled either by recirculation of condensed" tar or by Aintroduction oi fractionating column bottoms to give av desired tar gravity preferably less than 10 A. P. I. Both types of control are providedl for in the apparatus illustrated in Fig. '7. Thus,

tar'may be witlid'rawrfr from the bottom of the' flash tower through aline |69 and part of the tar forced throughv a pump |10 back into the flash tower with or without cooling in acooler |1I.

The ilash tower overhead |12 passes to a fractionating tower |13. IIere two gasoil cuts may be taken off-one as a side stream |14` and one as a bottom cut. 15. 'Either or both of these streams v'may be recycled through the system for further processing and may be returned to the tower syseither hot or cold, as desired. In the apparatus illustrated in Fig. 7, provision is made only for recirculation of thel bottom cut through a head product |84 or the receiver sl c. e., the portion of the fractionating column overhead which remains uncondensed) is withdrawn from this receiver and would contain a large portion4 of hydrocarbons which should be retained in the nal stabilized distillate. With this in mind, the overhead |84 from the receiver is passed through a compressor |85 'and compressed to a pressure slightly above that desired for stabilization. The

The distillate |88 from the high pressure receiver, i. e., the bottoms product or liquid resulting from the sepa-ration under high pressure, is sent to a conventional stabilizer '|89 from which a distillate |90 of the desired vapor pressure is drawn oil? as a bottoms product. q Overhead gas |9| from the stabilizer normally is divertedtogether with the overhead |92 from the high pressure receiver to a polymerization plant for con-4 version of these gases to higher olefin for poly-- mer gasoline.

I claim:

1. In the catalytic cracking of hydrocarbons involving the contact of a porous catalytic mass with vaporized hydrocarbons with resultant deposition of carbon on the mass and the 'subsequent treatment of the mass in an oxidizing atmosphere to burn the carbon and regenerate the mass withjfurther contact of the hydrocarbons,

the improvement which comprises rotating in the 1 -catalytic mass in the form of a plurality of separated catalyst beds of Isubstantial depth successively and substantially'continuously relative to and through a first zone to which thevaporized hydrocarbons are supplied substantially continuously and from which the resulting` cracked hydrocarbons-are substantially continuouslywithsubstantially continuously to remove products of l pump |16 and optionally either through a e001-,

ing coil' |11 ordirectly in the hot condition.

In the apparatus illustrated in Fig. .7 thev side stream cut is passed through the cooler |18 and thence is withdrawn from the system for further processing.

The overhead stream |18 of the fractionating tower is controlled to give a product withingasoline distillation range specifications. The over- \head from the fractionating column is withdrawn Jand passed through a cooler y|80 into a4 receiver |8I. .A portion of the condensed fractionator "overhead (receiver bottoms) |8|A may be re- .turned from this receiver as reilux to the top of. the fractionating column through a'pump |82 anda line |83 for -controlling the temperature of The apparatus of Fig. 'I is designed for low 4pressure operation, in which case a gaseous overdrawn, a second zone thfrough which a hot purg.-

ing gas is passed substantially continuously, a'

third zone through which a hot oxidizing gas is passed substantially continuously and in which the' carbon on the mass is oxidized. the resultiijig carbonaceous gases being withdrawn substantially continuously from said third zone, and a-fourth zone through which a' hot purging gasis passed the carbon combustion from the mass prior to the reintroduction thereof into the first zone.

2. In the catalytic.l cracking of hydrocarbons involving the contact of a porous catalytic mass with vaporized hydrocarbons with resultant dep.-

- osition of carbon on the mass and theY subsequent treatment of the mass in an oxidizing atmosi phere to burn the carbonv and regenerate the mass for further contact with the hydrocarbons,

the improvement which comprises rotating the catalyticmass in the form of a pluralityl of separated catalyst befs of substantial depth succes'- sively and substantially continuously relative to and through la first zone to which the vaporized hydrocarbons are supplied substantially continuously and from which the resulting cracked hydrocarbons are substantially continuously-withdrawn,- a second zone through which a hot purging gas is passed'substantially continuously, a

third zone through which a hot oxidizing gas is passed substantially continuously and in which the carbon on the mass is oxidized, the resulting carbonaceous gases being withdrawn substantially continuously from said third zone, and a fourth zone through which a hot purging gas is passed substantially continuously to remove products of the carbon combustion from the mass prior to the reintroduction thereof into the iirst zone, segments of said mass being disposed simultaneously in all four zones.

3. In the catalytic cracking of hydrocarbons involvingthe contact of a porous catalytic mass with vaporized hydrocarbons with resultant deposition of carbon on the mass and the subsequent treatment of the mass in an oxidizing atmosphere to burn the carbon and regenerate the mass for further contact with the hydrocarbons, the improvement which comprises rotating the catalytic mass in the\form of a plurality of sparated catalyst beds of substantial depth successively and substantially continuously relative to and through a iirst zone to which the vaporized hydrocarbons are substantially continuously supplied and from which the resulting cracked hydrocarbons-arei substantially continuously withdrawn, a second zone into which superheated Asteam is passed substantially continuously and from which the resulting mixture o'f superheated steam and hydrocarbons is withdrawn substantially continuously, a third zone through which a hotoxidizing gas is passed substantially continuously and in which the carbon on the mass is oxidized, the resulting carbonaceous gases being Withdrawn substantially continuously from said third zone, and a fourth zone into which l' superheated steam is introduced substantially continuously and from which theresulting mixture of superheated steam and carbonaceous gases is Withdrawn substantially continuously,

vthe catalytic mass being thereafter reintroduced into the rst zone.

4,. In the catalytic cracking of hydrocarbons involving the contact of a porous catalytic mass With vaporized hydrocarbons with resultant deposition of carbon on the mass and the subsequent treatment of the mass in an oxidizing atmosphere to burn the carbon and regenerate the mass for further contactwith the hydrocarbons, the improvement which comprises rotating n is passed substantially continuously and in which treatment of the mass in an oxidizing atmosphere to burn the carbon and regenerate the mass for further contact with the hydrocarbons, the improvement whichcomprises rotating the catalytic mass in the form `of a plurality of separated .catalyst beds of substantial depth successively and substantially continuously through a lirst zone to Which the vaporized hydrocarbons are continuously supplied and from which the resulting cracked hydrocarbons are continuously Withdrawn, a second zone throughwhich superheated steam is passed substantially continuously, a third zone to which a hot oxidizing gas is supplied substantially continuously and from whichk gaseous carbonaceous productsresulting from combustion of the carbon on the mass are removed substantially continuously, and a fourth zone through which superheated steam is passed.

substantially continuously for removing products of the carbon combustion from the mass prior to its reintroduction into the first zone, the temperature of the superheated steam supplied to cessively and substantially continuously-through a rst zone towhich the vaporized hydrocarbons are continuously supplied and from which the resulting cracked hydrocarbons are continuously Withdrawn, a second zone through which a hot purging fluid is passed substantially continuously, a third zone through which a hot oxidizing gas the carbon on the mass is oxidized. and a fourth zone through which a purging uid is passed substantially continuously for removing products of the carbon combustion from the mass prior to the catalytic mass in the form `of a plurality of separated catalyst beds of substantial depth -suc-` cessively and substantiallycontinuously through 'a first zone to which the vaporized hydrocarbons are continuouslysupplied from which the resulting cracked hydrocarbons are continuously Withdrawn, a second zone through which a purging gas is passed substantially continuofsly, a third zone to which a mixture of hot air and a hot substantially inert gas is passed substantially continuously and in ,which the carbon on the mass is oxidized, and a fourth zone through which a hot purging gas is passed substantiallv continuously for removing gaseous products of the carbon combustion from the mass prior to its reintroduction into the first zone. and correlating the speed rotationiof the catalytic mass andthe proportions of hot oxidizing gas and hot inert gasio. the mixture supplied to the third zonel to vary the proportion of carbon burned therein.

5. In the catalytic cracking of hydrocarbons involving the contact of a porous catalytic mass with vaporized hydrocarbons with resultant deposition of carbon on the mass and the\subseq'uent l said zones.`

its reintroductlon into the rst zone. and preventing leakage of gases from one zone to another by introducing into each of said zones from an outside source-la hot diluent gas having a pressure higher than the pressure prevailing in '7. In the catalytic cracking of hydrocarbons with vaporiz'ed hydrocarbons with resultant deposition of carbon on the mass and the subsequent treatment of the mass in an oxidizing atmosphere to burn the carbon and regenerate the mass for further contact with the hydrocarbons, the improvement which comprises rotating the catalytic mass in the form of a plurality of separated catalystabeds of substantial depth successively and substantially continuously through a rst zone through which the vaporized hydrocarbons are continuously supplied and from which the resulting cracked hydrocarbons are continuously Withdrawn, a second zone through which va purging fluid is passed substantially continuously, a third zone throughl which a hot oxidizing gas is passed substantially continuously and in which the carbonl on the ,mass is oxidized, and a fourth'zone through which a purgingf'fluid'ispassed substantially con-v tinuousiy for removing products of the carbon combustion from the mass prior' to its reintroduction into the first zone, mixing the resultin cracked hydrocarbons withdrawn from the firs zone with the mixture of purging fluid and hydrocarbons withdrawn from the second zone, and preventing admixture of a substantial part of the gaseous mixture discharged from the lthird and fourth zones with the cracked hydrocarbons withdrawn from the rst zone. l 4

8. In the catalytic cracking of hydrocarbons involving the contact of a porous catalytic mass with 'vaporized hydrocarbons with resultant 4, deposition of carbon on the mass and the subsequent treatment of the mass in an oxidizing atmosphere to burn the carbon and regenerate the mass for further contact with the hydrocarbons, the improvement which comprises rotatthe mass rs1'- further contact with the hydrocarbons, the improvement which comprises rotatingy vaporized hydrocarbons are continuously supplied and from which the resulting cracked hydrocaring the catalytic mass in the form of a plurality of separated catalyst beds of substantial depth successively and substantially continuouslyA relative to and through a first zone to which the vaporized hydrocarbons are continuously supplied' and from which the resulting cracked hydrocarbons are continuously withdrawn, a second zone through which s hot purging gas is passed substantially continuously, a' third zone through which a hot oxidizing gas is passed substantially continuously and in which the carbon on the involving thecontact of a porous catalyticrnass with vaporized hydrocarbons with resultant deposition oi' carbon on the mass and the sub- ,sequent treatment of the 4massl in an oxidizing atmosphere to burn the carbon and regenerate the mass for further contact with the hydrocarbons, the improvement which comprises rotating the catalytic mass in .the form of a plurality of separated catalyst beds of substantial depth successively and substantially continuously relative to and through a nrst zone toI which the vaporized hydrocarbons are continuously supplied Y and from which the resulting cracked hydrocarbons are substantially continuously withdrawn. a second zone through which a hot purging gas is passed substantially continuouslv. a third zone through which hot `oxidizing gesis passed substantially continuously and in which carbon on the 4mass -is oxidized. and a fourth zone through which a purging uid is passed substantially continuously for removing products oi' .the carbon combustion from the mass prior to its reintroduction into the first zone. the distance .traveled by the catalytic mass in passing through the first zone and the third zone, respectively, being substantially longer than the distances traveled by the catalytic mass in passing through the second and fourth zones, respectively.

. 10. In the catalytic cracking of hydrocarbons involving the contact of a porous catalytic mass with vaporized hydrocarbons with resultant deposition of carbon on the mass and the subsequent treatment of the mass in an oxidizing bons are continuously withdrawn, a second zone through which a hot purging gas is passed substantially continuously, a third zone through whichhot1oxidizing gas is passed substantially continuously and in whiclrthe carbon on the mass is oxidized, and a fourth zone through which a purging fluid is passed Vsubstantially continuously for removing products of the carbon combustionfrom th mass prior to its reintroduction into the first zone and varying the time of the cycle required for passing' the catalytic mass through the four zones by varyingl the speed of rotation of the catalyst.

b 11. In the catalytic cracking of hydrocarbons involving the contact of a porous catalytic mass with vaporized hydrocarbons with resultant deposition of carbon on the mass and the subsequent treatment ofthe mass in an oxidizing atmosphere to burn the'carbon and regenerate the mass for further contact with the hydrocarbons, 'the improvement which comprises rotating the catalytic mass-in the form of a plurality of separated catalyst beds of substantial depth successively 'and substantially continuously through a first zone to which the vaporized hydrocarbons are continuously supplied and lfrom which the resulting cracked hydrocarbons are i continuously withdrawn, a second zone through which a purging fluid is passed substantially continuously, a third zone through which a hot and afourth zone through which a purging'nuid is passed substantially continuously for removing products of the carbon combustion from the.

mass prior to its reintroduction into the first zone. the catalytic mass being divided into a plurality of segments, and in each of said zones terminating the passage of fluid in contact with any one segmentl of the catalytic'mass before commencing the passage of the fluid supplied to the next succeeding zone in contact with such segment.

12. .Tn the catalytic cracking ofhydrocarbons involving the contact of a porous catalytic mass with vaporized hydrocarbonsn with resultant deposition of carhonon the mass and the subseouent treatment of the mass in an oxidizing atmosphere to burn'the carbon and regenerate the mass for further contact with the hydrocarbons. the improvement which comprises rotating atmosphere to burn the carbon and regenerate ing gas is passed substantially continuously,4 a

third zone'through which hot oxidizing gas is passed substantially continuously and in which l the-carbon on the mass is oxidized, and a fourth zone through which ahot purging, gas is passed substantially continuously forremoving products A of the carbon combustion from the mass prior to its reintroduction into the rst zone, the pressure of gas in the second and fourth zones being maintained in slight excess of the pressure of gas in the rst and third zones.

13. In the catalytic cracking of hydrocarbons involving the contact of a porous catalytic mass with vaporized hydrocarbons with resultant deposition of carbon on the mass and-the subsequent treatment of the mass in an oxidizing atmosphere to burn the carbon and regenerate the mass for further contact with the hydrocarbons, the improvement which comprises rotating the catalytic massV in the form of a plurality of separated catalyst beds of substantial depth successively and substantially continuously through a iirst zone to which the vaporized hydrocarbons are continuously supplied and from which thevresulting cracked hydrocarbons are"y continuously withdrawn, a second zone through which a hot purging gas is passed substantially l continuously, a'third zone through which hot l oxidizing gas diluted with a hot inert gas is passed substantially continuously and in which the carbon on the mass is oxidized, the fourth 4zone through which a purging fluid is passed OLIVER F; CAMPBELL. 

